Imogolite is an aluminium silicate clay mineral with the chemical formula Al2SiO3(OH)4. It occurs in soils formed from volcanic ash and was first described in 1962 for an occurrence in Uemura, Kumamoto prefecture, Kyushu Region, Japan. Its name originates from the Japanese word imogo, which refers to the brownish yellow soil derived from volcanic ash. It occurs together with allophane, quartz, cristobalite, gibbsite, vermiculite and limonite.
|Crystal system||Tetragonal |
Unknown space group
|Color||White, blue, green, brown, black|
|Crystal habit||Conchoidal to earthy masses of microscopic threadlike particles and bundles of fine tubes, each about 20 Å in diameter|
|Mohs scale hardness||2–3|
|Luster||Vitreous, resinous, waxy|
|Diaphaneity||Transparent to translucent|
Imogolite consists of a network of nanotubes with an outer diameter of ca. 2 nm and an inner diameter of ca. 1 nm. The tube walls are formed by continuous Al(OH)3 (gibbsite) sheets and orthosilicate anions (O3SiOH groups). Owing to its tubular structure, natural availability, and low toxicity, imogolite has potential applications in polymer composites, fuel gas storage, absorbents, and as a catalyst support in chemical catalysis.